Jerry G. wrote:
When using dual magnetrons, there has to be a consideration for their
phase correction.

Magnetrons will always phaselock to any signal that is back fed into them,
provided it is close to their own natural resonant frequency. So, the two
magnetrons will reach a compromise and oscillate, in phase, at some frequency
between their natural resonances.

-Chuck Harris

If there is any shared area of radiation, and if there
is any phase shift between them that is leading to being out of phase,
there will be some wasted energy. This would cause them to be
cancelling each other, rather than be summing their energy outputs to
the target, which is the food inside the microwave oven. The wasted
energy would be causing the magnetrons and the power supply to run
hotter, and thus become less efficient.

As for home use, when considering that these systems are working at
about 900 to 1200 Watts each, depending on the type and model, having 2
magnetrons would be a bit much.